The present invention relates to a method of producing magnetic powders from heavy metal sludges, in particular, to a method of producing magnetic powders by adding an adequate stoichiometric amount of ferric compounds to heavy metal sludges and controlling the temperature and atmosphere, the heavy metal sludges are converted into ferrite powders having a strong magnetic characteristic.
The sources of heavy metal sludges come from the treatments of waste water containing heavy metals. Waste water containing heavy metals is usually obtained from the effluent liquids of electroplating industry, acid treatment of waste hardware, treatment of metal surface membrane such as the treatment of chlorate membrane, anode treatment, and phosphate treatment. For environmental protection reasons, these effluent liquids should be adequately treated before they are discharged into drains. Currently, the neutralizing precipitation method includes the steps of precipitating heavy metals to form sludges and discharging solution under effluent standards for environmental requirements. However, the accumulative amount of formed sludges is very large. The formed sludge will produce serious treatment problems because the sludges contain heavy metal components which may be toxic. If the heavy metal sludges are buried, quite a large area for storage is required. Moreover, the heavy metal sludges normally contain hydroxide, and the heavy metals will immediately dissolve out after its contacting with acid solution
The present invention is to provide a low cost and economical technology for treating the heavy metal sludges of which traditional treatment requires high cost or high difficulty. The method according to the present invention is directed to the adding of ferric compounds, e.g., ferric hydroxide or ferric oxide to the heavy metal sludges, mixing homogeneously under an atmosphere control and at adequate temperature so as to convert heavy metal sludges into ferrite powders with strong magnetism. The present technology not only converts wastes originally requiring difficult treatments into magnetic powders, but also is widely applied in waste water treatments for the purpose of re-utilizing and avoiding serious pollutions caused by such a large amount of heavy metal sludges.